PHENOMENA OP MUSCLE. 239 



Among- these difficulties may be mentioned the difference in 

 strength of the polarisation-currents according to the direction of 

 the stimulating current in the pair of muscles, and the fact that 

 the relations of the polarisation-currents led off from the upper 

 half of the muscle are in some respects the reverse of those led off 

 from the lower half. Another question is, why the positive polar- 

 isations in each half are stronger when the stimulating current 

 flows from the equator towards the extremity, than when it flows 

 in the opposite direction, and why the reverse is not the case ? and 

 why, further, all secondary actions are stronger in the lower half of 

 the muscle than in the upper? why very strong descending currents 

 (30 to 40 Groves) with closing times of 20 sees. I min., 5 niins. 

 again give positive variation, ascending currents negative variation, 

 and so on ? For each of these questions I could find an answer based 

 on the experience I have gained in working with the sartorius. 

 That such answers would be correct as regards the pair of muscles in 

 question, could only be proved by the aid of numerous and varied 

 researches on them. I cannot however regard it as my task to 

 institute a tedious series of researches under such complicated con- 

 ditions as those offered by du Bois-Reymond's preparation. Such 

 researches could at best only lead by a long and circuitous path to 

 such a knowledge of the same laws as is afforded directly by the 

 study of a regularly constructed muscle. 



With the observation just mentioned, that with certain current 

 strengths and closing times the positive polarisation was stronger 

 in each half of the muscle when the current flowed in that half 

 from the equator to the end, du Bois-Reymond connects the suppo- 

 sition that this phenomenon stands in relation to the circumstance, 

 that in natural stimulation of a muscle through the nerve, the 

 excitation spreads from the neighbourhood of the equator where the 

 nerve-filaments enter the muscle-fibres, towards both ends. Hence 

 he infers that the direction in which normally the proper physiolo- 

 gical changes are propagated in muscle-fibres is the most favourable 

 likewise for positive polarisation. 



It is not however clear how the observations of du Bois-Reymond 

 on his muscle-preparation could lead to such a supposition. For 

 each muscle of the pair, on account of the tendinous intersections, 

 consists functionally of two separate muscles. With regard to the 

 rectus internus major or gracilis this is strictly true ; with regard 

 to the semimembranosus, it is at least partly so, for only some 

 of its fibres run the whole length of the muscle, all the others 



